Intelligence

Psychometrics
◦ Subarea of psychology
◦ Concerned with developing psychological tests that
assess an individual’s abilities, skills, beliefs, and
personality traits in a wide range of settings
 school
 industry
 clinic

Two-factor theory
◦ Developed by Charles Spearman
◦ Says that intelligence has two factors
 general mental ability factor “g”; represents what
different cognitive tasks have in common
 specific factors “s”; include specific mental abilities
such as mathematical, mechanical, or verbal skills

Multiple-intelligence theory
◦ Developed by Howard Gardner
◦ Instead of one kind of general intelligence, there
are at least seven different kinds, including
 verbal intelligence
 musical intelligence
 logical mathematical intelligence
 spatial intelligence
 body movement intelligence (to understand oneself)
 intelligence to understand others

Triarchic theory
◦ Developed by Robert Sternberg
◦ Says that intelligence can be divided into three
different kinds of reasoning processes
 uses analytical or logical thinking skills measured by
traditional intelligence tests
 uses problem-solving skills that require creative
thinking and the ability to learn from experience
 uses practical thinking skills that help a person
adjust to, and cope with, his or her sociocultural
environment
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Early attempts to measure intelligence
◦ Head size and intelligence
◦ Francis Galton
 noticed that intelligent people often had intelligent
relatives and concluded that intelligence was, to a
large extent, biological or inherited
 low correlation between head size and intelligence
 using head size as a measure of intelligence was
abandoned in favor of using skull or brain size

Early attempts to measure intelligence
◦ Brain size and intelligence
 Paul Broca
 claimed there was a relationship between size of brain
and intelligence
 larger brains indicating more intelligence
 later reanalysis of Broca’s data indicted that measures
of brain size proved to be unreliable and poorly
correlated with intelligence
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Early attempts to measure intelligence
◦ Brain size and achievement
 enormous variation in brain size and achievement
◦ Brain size, sex differences, and intelligence
 female brains weigh about 10% less than male brains
 little or no difference in intelligence between men and
women
 larger size of men’s brains doesn’t result in higher IQs

Binet’s breakthrough
◦ Alfred Binet
 Believed intelligence was a collection of mental
abilities; best way to assess it was to measure a
person’s ability to perform cognitive tasks
 Binet-Simon Intelligence Scale
 contained items arranged in order of increasing difficulty
 measured vocabulary, memory, common knowledge, and
other cognitive abilities
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Binet’s breakthrough
◦ Binet and Simon revised their intelligence scale to
solve several problems in their original scale
◦ Mental age
 method of estimating a child’s intellectual progress by
comparing his or her score on an intelligence test to
the scores of average children of the same age

Formula for IQ
◦ Intelligence quotient
 computed by dividing a child’s mental age (MA), as
measured in an intelligence test, by the child’s
chronological age (CA) and multiplying the result by
100
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Wechsler Intelligence Scale
◦ Most widely used IQ tests
◦ Wechsler Adult Intelligence Scale (WAIS-III), ages 16
and older
◦ Wechsler Intelligence Scale for Children (WISC-III)
for children ages 3 to 16
◦ Both have items organized into various subtests
 verbal section
 performance section
 verbal and performance combined give a single IQ
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Two characteristics of tests
◦ Validity
 means that the test measures what it’s supposed to
measure
◦ Reliability
 refers to consistency: score on a test at one point in
time should be similar to the score obtained by the
same person on a similar test at a later point in time

Normal distribution of IQ scores
◦ Normal distribution
 refers to a statistical arrangement of scores so that
they resemble the shape of a bell and, thus, is said to
be a bell-shaped curve
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Mental retardation: IQ scores
◦ Mental retardation
 substantial limitation in functioning characterized by
significantly subaverage intellectual functioning, along
with related limitations in 2 of 10 areas, including
communication, self-care, home living, social skills,
and safety
 borderline mentally retarded: IQs from 50 to 75
 mildly/moderately mentally retarded: IQs from 35
to 50
 severely/profound mentally retarded: IQs from 20
to 40
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Mental retardation: IQ scores
◦ Causes
 Organic retardation
 results from genetic problems or brain damage
 Cultural-familial retardation
 results from a greatly impoverished environment
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Vast majority: IQ scores
◦ about 95%, have scores that fall between 70 and
130

Gifted: IQ scores
 moderately gifted
 usually defined by an IQ score between 130 and 150
 profoundly gifted
 usually defined by an IQ score around 180 or above
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Binet’s warnings
◦ Intelligence tests don’t measure innate abilities or
natural intelligence
◦ Intelligence tests, by themselves, shouldn’t be used
to label people
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Cultural bias
◦ The wording of the questions and the experiences
on which the questions are used
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Nonintellectual factors
◦ Refer to noncognitive factors, such as attitude,
experience, and emotional functioning, that may
help or hinder performance on tests

Definition
◦ Asks how nature (hereditary or genetic factors)
interacts with nurture (environmental factors) in the
development of a person’s intellectual, emotional,
personal, and social abilities

Twin studies
◦ Fraternal twins
 siblings (brothers and sisters) who develop from
separate eggs and have 50% of their genes in common

Twin studies
◦ Identical twins
 develop from a single egg and thus have identical
genes (have 100% of their genes in common)
◦ Interaction of nature and nurture
 when researchers report that genetic factors influence
intelligence (IQ scores), it means that genetic factors
influence cognitive abilities to varying degrees,
depending on the environment

Adoption studies
◦ Children with limited social-educational
opportunities and low IQs were adopted by parents
who could provide increased social-educational
opportunities
◦ Studies show that children with poor educational
opportunities and low IQ scores can show an
increase in IQ scores when adopted into families
that provide increased educational opportunities

Interaction: nature and nurture
◦ Heritability
 number that indicates the amount or proportion of
some ability, characteristic, or trait that can be
attributed to genetic factors (nature)
◦ Reaction range
 indicates the extent to which traits, abilities, or IQ
scores may increase or decrease as a result of
interaction with environmental factors